1. Field of the Invention
The present invention relates to tide gate valves, and, in particular, to inversion resistant support devices for tide gate valves.
2. Description of the Prior Art
A tide gate valve is essentially a valve which allows fluid to flow in only one direction through a conduit, while closing and preventing back or reverse flow, when back pressure builds up downstream of the valve to a level greater than the upstream fluid pressure head.
As shown in FIGS. 1-4, the basic structure of a tide gate valve 10 includes an inlet end 14, called a cuff, an outlet end 16, called a bill, and a transition part 18, called a saddle. The inlet end 14 is normally a tubular structure that is securedly attachable to the end of a pipe in a drainage system. Attached to the inlet end 14 is the transition part 18, which, when connected to the inlet end 14, tapers outward on its vertical axis and inward on its horizontal access. The resulting shape of the transition part is likened to a duck-bill and is constructed from a flexible, pliable material, such as rubber. At the end of the transition part 18 is a slit-shaped outlet end 16, which allows the flow of a liquid material through the outlet end 16. Projecting outward from the end of the outlet end 16 are two vertical lips 21 which define a vertical slit 20.
In normal operation, when fluid is flowing through a piping system outlet 12 into the tide gate valve 10, the fluid enters through the inlet end 12 and proceeds to the transition part 18. Fluid then enters the outlet end 16 and exits through the vertical slit 20 formed by the two vertical lips 21. The pliability of the transition part 18 allows the fluid to easily flow through the vertical slit 20, and, if any back pressure or back flow is encountered, the shape of the transition part 18 clamps the two vertical lips 21 together, disallowing back flow. However, as the transition part is made of a pliant material, too much back pressure will cause the transition part 18 to buckle in upon itself, separating the two vertical lips 21 and widening the vertical slit 20. This, in turn will allow fluid to enter through the outlet end 16 and back again through the tide gate valve 10 into the inlet end 14 and piping system outlet 12.
In order to overcome this possible tide gate valve failure, fabric reinforcing plies may be used to increase the strength and stiffness of the valves. As demonstrated in U.S. Pat. No. 4,585,031 to Raftis et al., a multiple-ply sleeve, in combination with a rigid support member provides inversion resistance in a tide gate valve application. U.S. Pat. No. 4,607,663 to Raftis et al. teaches the usage of staggered embedded pads to provide sufficient strength for inversion and sagging resistance in a tide gate valve application. Using lengthened lips connected to a sleeve area has been proposed to increase inversion resistance, as demonstrated in U.S. Pat. No. 5,606,995 to Raftis. Finally, U.S. Pat. No. 5,769,125 discloses a check valve, which includes a hinge and trough construction, which is also an inversion deterrent.
While the prior art uses some form of reinforcement against possible inversion, the designs in the previously-mentioned patents are still believed to be deficient in withstanding immediate or sudden high pressure back flow. Further, the prior art can only provide increased inversion protection at the cost of increased pressure drop in the forward direction of flow. In essence, the trade off of inversion resistance as against head loss requires great improvement.
It is therefore an object of this invention to overcome the design problems associated with prior art rubber tide gate valves. It is another object of this invention to maximize valve resistance to back pressure without sacrificing pressure drop in the required flow direction.
The present invention relates to a backflow prevention system generally including a tide gate valve, such as a duck-billed type of valve, and a support structure. The tide gate valve generally includes an inlet end, a transition part or saddle connected to the inlet end, an outlet end positioned adjacent to the saddle, and an inner surface which defines an internal cavity that fluidly connects the inlet end and the outlet end. The support structure generally includes a bearing surface positioned adjacent the inner surface of the tide gate valve in the area of the transition part and at least one opening for fluid flow through the support structure. The support structure is receivable in the internal cavity of the tide gate valve and preferably extends through the inlet end and into the saddle, with the bearing surface at least in part engageable by the inner surface of the tide gate valve.
The support body can be a pipe end, a cylindrical ring having an upstream end and a downstream end engageable on a pipe end, a cage, or other suitable device. A flange may be positioned on the upstream first end of the cylindrical ring, with the flange engageable with a mating flange on a pipe end. At least one support arm may extend from the downstream end of the cylindrical ring, such as two inwardly directed support arms. A plate may be positioned on the cage.
The exterior shape of the support body may be generally in the shape of a cone, a truncated cone, a shortened or dulled hollow conical shape, a cylindrical shape, a cage-like shape, a conical shape, or other suitable shape.
The invention itself, both as to its construction and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings.